To date, many “agglutination” methods have already been proposed. They are mainly used for detecting antigens and/or antibodies for diagnostic purposes. These methods are in particular applied for bioassays (pregnancy tests, clotting tests) or the diagnosis of infectious diseases. However, these methods generally have a limited sensitivity. In fact, the general principle of these tests consists in detecting the formation of a gel of colloidal particles which forms in the presence of the analyte. In this type of test, the analyte must be able to attach two colloidal particles, the surfaces of which are covered with a molecule which recognizes, in the broadest sense, the analyte to be assayed.